@pheasantplucker/failables

failables

Failables are a clean, consistent, async-friendly, network-friendly result type.

Successful results are represented as failables of type SUCCESS, with the result stored in the payload.

Empty results are neither success nor failure; they are represented as failables of type EMPTY, and of course have no payload. Calling success without a payload will result in an empty failable (not a success).

Instead of representing errors sometimes by a result code, sometimes by a magic number, and sometimes by throwing an exception, consistently represent errors as failables of type FAILURE, with the error message stored in the payload.

That's all there is to it.

usage

  const result1 = success('foo') // first parameter is payload
  const result2 = success('foo', { timesCalled: 7 })  // second (optional) parameter is metadata
  const result3 = failure('trouble!') // payload is error message
  const result4 = failure('trouble!', { userId: 'fred' })  // all failables can include metadata
  const result5 = empty() // empty failables have no payload
  const result6 = empty({ userId: 'fred' })  // for empty, the first (optional) parameter is metadata

  const answer = payload(result1) // extract the payload
  const metadata = meta(result2) // extract the metadata
  if (isFailure(result4)) return result4 // a common pattern: if a failure is encountered in a
                                         // failable-returning function, just return the failure directly

documentation

creation

  success(payload, meta) // returns a success failable
  failure(payload, meta) // returns a failure failable
  empty(meta)            // returns an empty failable

tests

  isFailable(object)  // whether the object represents a failable
  isSuccess(failable) // whether the failable is success
  isFailure(failable) // whether the failable is failure
  isEmpty(failable)   // whether the failable is empty

elements

  payload(failable) // extracts the failable's payload
  meta(failable)    // extracts the failable's metadata

list operations

  anyFailed(list)            // whether any in the list failed
  firstFailure(list)         // the first failure in the list
  extractPayloads(failables) // extracts the payloads from a list of failables
  flattenResults(list)       // return the first failure, if any, or the extracted payloads

assertions

  assertSuccess(failable, payload)        // assert that the failable is success
  assertSuccessWhich(predicate, failable) // assert that the failable is success
                                          // and its payload satisfies the predicate
  assertSuccessTyped(type, failable)      // assert that the failable is success
                                          // and the payload has the named type
                                          // ('string', 'number', 'object', 'boolean')
  assertFailure(failable, payload)        // assert that the failable is failure
  assertEmpty(failable)                   // assert that the failable is empty

utility

  hydrate(failable) // returns an object with kind, payload, and meta fields